Analysis of Variable Amplitude Fatigue Data of the P355NL1 Steel Using the Effective Strain Damage Model

Abstract

This paper proposes an analysis of variable amplitude fatigue data obtained for the P355NL1 steel, using a strain-based cumulative damage model. The fatigue data consist of constant and variable amplitude block loading, which was applied to both smooth and notched specimens, previously published by the authors. The strain-based cumulative damage model, which has been proposed by D.L. DuQuesnay, is based on the growth and closure mechanisms of microcracks. It incorporates a parameter termed net effective strain range, which is a function of the microcrack closure behavior and inherent ability to resist fatigue damage. A simplified version of the model is considered, which assumes crack closure at the lowest level for the entire spectrum and does not account for varying crack opening stresses. In general, the model produces conservative predictions within an accuracy range of two on lives, for both smooth and notched geometries, demonstrating the robustness of the model.

A non-linear damage accumulation fatigue model for predicting strain life at variable amplitude loadings based on constant amplitude fatigue data

“…The method is validated using data from experiments performed on P355NL1 steel, 304L stainless steel, and 7075 T6 aluminum. [20,21] The present model fits the experimental data well for a variety of load spectra and materials and the algorithm is simple to implement.…”

“…Published experimental data are used to validate the model. [20,21] Pereira et al tested P355NL1 steel and compared their experimental results to an effective strain damage model based on the work of DuQuesnay. [20] Colin and Fatemi published experimental data for 304L stainless steel and 7075 T6 aluminum.…”

“…[20,21] Pereira et al tested P355NL1 steel and compared their experimental results to an effective strain damage model based on the work of DuQuesnay. [20] Colin and Fatemi published experimental data for 304L stainless steel and 7075 T6 aluminum. [21] The load histories used in the calculations were recreated from the descriptions detailed by Pereira et al, and Colin and Fatemi.…”

“…[21] The load histories used in the calculations were recreated from the descriptions detailed by Pereira et al, and Colin and Fatemi. [20,21] The P355NL1 specimens were subjected to a variety of load blocks, including a high to low scheme, a low to high scheme, a low to high to low scheme, and random loading, examples of which are shown in Figs. 1, 2, 3, and 4.…”

“…The model described in section 2 above was implemented using the algorithm detailed in this section and applied to the strain history data discussed in section 3. To begin, the first two strains from the strain history were converted to stresses using the Figure 3: An example of a low to high to low strain loading block after the work of Pereira et al [20] Ramberg-Osgood stress-strain relationship,…”